A Novel Single Layer Wideband Reflectarray Design Using Two Degrees of Freedom Elements

A broadband linearly polarized single-layer reflectarray antenna constructed with element cells of spiral-dipoles is presented in this communication. The proposed method achieves the phase change requirements by continuously adjusting the two degrees of freedom (TDF) elements. Then, a linear and smooth phase response covering 360 degrees is obtained by adjusting the TDF. Furthermore, by introducing four rectangular rings around the spiral-dipoles, a relatively slow phase change slope can be obtained and the maximum differences between the achieved phase acquired by element and ideal phase at 6.5 and 9.5 GHz are 20 degrees and 58 degrees, respectively, enlarging the operating bandwidth. A reflectarray prototype with a rectangular aperture of 300 mm in diameter is designed, fabricated, and experimentally verified. The results include a measured gain of 26.5 dBi at 8 GHz with an aperture efficiency of 55%; the 1 dB gain bandwidth can reach 35%. The proposed structure can be extrapolated to higher frequencies due to its single-layer performance. Its benefits include a reduction in manufacturing costs and the mitigation of alignment errors.